1. Field of the invention
The present invention is a wind turbine generator and relates to a wind turbine having a plurality of blades attached to a rotor, the rotating force generated by allowing wind force to act on the blades being transmitted to the output shaft of the rotor, wherein a controller of an active annular plane area is provided for making it possible to change the active annular plane area of the wind turbine by reciprocating each of the blades in a radial direction or by slanting the rotor and the operating method thereof.
2. Description of the Related Art
A wind turbine power plant having high capacity of generating electric power by installing a plurality of wind turbine electric power generator units, each of which utilizes the rotating force generated by applying wind force to a plurality of blades attached to a rotor to drive a generator via the wind turbine shaft, is constructed at high elevation such as the top of a hill or mountain or at a place where high wind velocity can be received, such as above the sea.
The wind turbine apparatus used for driving an electric generator or other purposes is constructed, as shown in FIG. 1 of patent document 1 (Japanese Patent Application Publication No. 5-60053) and In FIG. 1 of patent document 2 (Japanese Patent Application Publication No. 5-60053)), such that a plurality of blades are attached to the periphery of a rotor head and the rotating force generated by wind force is transmitted to the turbine shaft via the rotor head. Desired or determined electric power generation is maintained by changing the pitch angle of the blades attached to the rotor in accordance with the wind speed and required electric power while controlling to adjust the blade pitch angle to the angle optimal for the wind speed blowing when the apparatus is in operation.
In the wind turbine of FIG. 1 of patent document 3 (Japanese Patent Application Publication No. 2001-99045), blades are attached to a rotor head such that the blades are supported for rotation via bearings fixed to the rotor head, bevel gear mechanism is provided inside the rotor head to be driven by a servomotor. The pitch angle of the blades is changeable by rotating the blades relative to the rotor head by the servomotor via the bevel gear mechanism.
The output power of the wind turbine generated by the action of wind is about proportional to active annular plane area, i.e., the area of the annular plane formed between the circumscribed circle of the blade tips and the inscribed circle of the blade roots.S=π(L2−I2)  (1)where S is active annular plane area, L is radius of the circumscribed circle, and I is radius of the inscribed circle.
In order to increase the output power of a wind turbine, it is required that radius L is increased or the difference between L and I, that means the length of the blade is increased.
The power Pw that the wind passing through active annular plane area S has, isPw=k·S·V3  (2)where V is wind speed, and k is air density divided by 2.
As wind speed depends on weather conditions at the location of the wind turbine, the output of the wind turbine, that is the electric power generated in the case of wind turbine electric generator, can be increased by increasing the active annular plane area.
However, in the case where the active annular plane area is increased for increasing output power, the rotating components such as the blades and rotor are more likely to be broken by fatigue failure resulting from being subjected to repeated excessively fast wind speed V of a gust of wind, etc., which sometimes occurs according to weather conditions, although the output is increased.
With the prior art disclosed in patent documents 1 and 2, because the blades are fixed to the rotor head of a somewhat larger diameter than the rotor shaft, it is difficult to design a longer blade, that is, to increase radius L, so that there is a limit for increasing the output of a wind turbine. Further, when blade length is increased to the maximum to increase active annular plane area for increasing the output of the wind turbine, the rotating components such as the blades and rotor tend to be broken by fatigue failure due to repeated occurrence of a gust of wind, etc., of excessively increased speed.
The wind turbine of patent document 3 has a means for changing blade pitch angle by rotating the blades relative to the rotor head, however, the active annular plane area is not variable but constant, and there remains also the problem that the rotating components such as the blades and rotor tend to be broken by fatigue failure resulting from being subjected to repeated excessively increased speed of a gust of wind, etc.